Clarify the support status of NIO1 (#1949)

Motivation:

It's currently unclear that SwiftNIO1 is end of life.

Modifications:

Update the README to set a deadline on patches to NIO1

Result:

Everyone knows where the core team stands on supporting NIO1

Co-authored-by: George Barnett <[email protected]>

README.md

@@ -11,14 +11,14 @@ It's like [Netty](https://netty.io), but written for Swift.
 
 The SwiftNIO project is split across multiple repositories:
 
-Repository | NIO 2 (Swift 5.2+) | NIO 1 (Swift 4+)
---- | --- | ---
-[https://github.com/apple/swift-nio][repo-nio] <br> SwiftNIO core | `from: "2.0.0"` | `from: "1.0.0"`
-[https://github.com/apple/swift-nio-ssl][repo-nio-ssl] <br> TLS (SSL) support | `from: "2.0.0"` | `from: "1.0.0"`
-[https://github.com/apple/swift-nio-http2][repo-nio-http2]<br> HTTP/2 support | `from: "1.0.0"` | `from: "0.1.0"`
-[https://github.com/apple/swift-nio-extras][repo-nio-extras] <br>useful additions around SwiftNIO | `from: "1.0.0"` | `from: "0.1.0"`
-[https://github.com/apple/swift-nio-transport-services][repo-nio-transport-services] <br> first-class support for macOS, iOS, tvOS, and watchOS | `from: "1.0.0"` | `from: "0.1.0"`
-[https://github.com/apple/swift-nio-ssh][repo-nio-ssh] <br> SSH support | `.upToNextMinor(from: "0.2.0")` | _n/a_
+Repository | NIO 2 (Swift 5.2+)
+--- | ---
+[https://github.com/apple/swift-nio][repo-nio] <br> SwiftNIO core | `from: "2.0.0"`
+[https://github.com/apple/swift-nio-ssl][repo-nio-ssl] <br> TLS (SSL) support | `from: "2.0.0"`
+[https://github.com/apple/swift-nio-http2][repo-nio-http2]<br> HTTP/2 support | `from: "1.0.0"`
+[https://github.com/apple/swift-nio-extras][repo-nio-extras] <br>useful additions around SwiftNIO | `from: "1.0.0"`
+[https://github.com/apple/swift-nio-transport-services][repo-nio-transport-services] <br> first-class support for macOS, iOS, tvOS, and watchOS | `from: "1.0.0"`
+[https://github.com/apple/swift-nio-ssh][repo-nio-ssh] <br> SSH support | `.upToNextMinor(from: "0.2.0")`
 
 NIO 2.29.0 and older support Swift 5.0+.
 
@@ -64,22 +64,26 @@ APNS | ✅ | ❌ | [kylebrowning/APNSwift](https://github.com/kylebrowning/APNSw
 PostgreSQL | ✅ | ❌ | [vapor/postgres-nio](https://github.com/vapor/postgres-nio) | `PostgresNIO` | SSWG community project
 Redis | ✅ | ❌ | [mordil/swift-redi-stack](https://gitlab.com/Mordil/swift-redi-stack) | `RediStack` | SSWG community project
 
-### Supported Platforms
+### Supported Versions
 
-SwiftNIO aims to support all of the platforms where Swift is supported. Currently, it is developed and tested on macOS and Linux, and is known to support the following operating system versions:
+### SwiftNIO 2
+This is the current version of SwiftNIO and will be supported for the forseeable future.
 
-* Ubuntu 18.04+
-* macOS 10.9+, iOS 7+; (macOS 10.14+, iOS 12+, tvOS 12+ or watchOS 6+ with [swift-nio-transport-services][repo-nio-transport-services])
+The latest released SwiftNIO 2 version supports Swift 5.2+. NIO 2.29.0 and older support Swift 5.0+.
 
-### Swift versions
+### SwiftNIO 1
+SwiftNIO 1 is considered end of life - it is strongly recommended that you move to a newer version.  The Core NIO team does not actively work on this version.  No new features will be added to this version but PRs which fix bugs or security vulnerabilities will be accepted until the end of May 2022.
 
-#### SwiftNIO 1
+If you have a SwiftNIO 1 application or library that you would like to migrate to SwiftNIO 2, please check out the [migration guide](docs/migration-guide-NIO1-to-NIO2.md) we prepared for you.
 
 The latest released SwiftNIO 1 version supports Swift 4.0, 4.1, 4.2, and 5.0.
 
-#### SwiftNIO 2
+### Supported Platforms
 
-The latest released SwiftNIO 2 version supports Swift 5.2, 5.3, and 5.4. If you have a SwiftNIO 1 application or library that you would like to migrate to SwiftNIO 2, please check out the [migration guide](docs/migration-guide-NIO1-to-NIO2.md) we prepared for you.
+SwiftNIO aims to support all of the platforms where Swift is supported. Currently, it is developed and tested on macOS and Linux, and is known to support the following operating system versions:
+
+* Ubuntu 18.04+
+* macOS 10.9+, iOS 7+; (macOS 10.14+, iOS 12+, tvOS 12+ or watchOS 6+ with [swift-nio-transport-services][repo-nio-transport-services])
 
 ### Compatibility